catch exceptions as const

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I3a2943bbae131c4528a9bc487524beb31e850357
diff --git a/src/gpio.cpp b/src/gpio.cpp
index 05b8e15..28eef92 100644
--- a/src/gpio.cpp
+++ b/src/gpio.cpp
@@ -104,7 +104,7 @@
             return true;
         }
     }
-    catch (std::exception& e)
+    catch (const std::exception& e)
     {
         log<level::ERR>("Error parsing GPIO JSON", entry("ERROR=%s", e.what()),
                         entry("GPIO_NAME=%s", gpioName.c_str()));
@@ -138,7 +138,7 @@
                             entry("GPIO_NAME=%s", gpioName.c_str()));
         }
     }
-    catch (std::exception& e)
+    catch (const std::exception& e)
     {
         log<level::ERR>("Error parsing GPIO JSON", entry("ERROR=%s", e.what()),
                         entry("GPIO_NAME=%s", gpioName.c_str()));